Dougie, did you Inspect the pitches or Vans, if brand new they should come from the manufacturer with "Cert". Usually NICEIC or all the ones that I have ever come across have.

6mm bonds not an issue as others have stated as caravan pitches are usually supplied in alcothene for the water and the gas is bottled so wouldn't normally require bonding either as the hoses the bottles attach to are rubber.

Unusual for the pitches to be non "TT" are you sure, I look after a 174 pitch site and it is TT but for most of the park the Ze of the pitches are around 0.30 ohms with the exception of the pitches that are on shellet as very little moisture is retained in that type of ground and it is a problem getting anything below 120 ohms, not even adding the "Salts" helps

15m not an issue either IMO as long as it is supplied in flex with a plug and socket arrangement with a minimum csa of 2.5mm (Iprefer 4mm for longer runs) and not greater than 16amps / 30mA whats the worry ?? I would be worried if the pitches are PME /TNC-S as that is a deffo NO NO.

Just a thought, though I don't have vast mobile/park home experience - If they are metal skinned is there always an earth connection to the metallic outer? Although there is usually a metal chassis, it, the skin, and internal earthed accessories are usually fixed to a wooden frame?

If there is no usual access to someone in contact with the general mass of earth and earthed metallic parts of the unit then PME connection may be OK: for example see page 25 item (e):

Supply not TT, fed from these caravan meters, I looked at dozens of these looking for rod, took various as at pitches some as over 300ohms.

Problem, A bit high but if your working to the NICEIC recomendation then you will know about the 200ohm recomendation etc what is the supply can you verify, it may well be TT but no earth rods visible, If intalled on just RCD's someone may have just assumed the 1667 ohms allowable on a 30mA and left it at that

These new ans didn't come with EIC cert that I though odd. Wired in twin and search called Kalbo or something like that (is that not the recalled cable from service).

Kablo cheap T+E with a figure of 8 instead of twin, The pitches from the RCD into the van are in twin ?? if so incorrect read through section 708 of the BGB

Poor joint boxes with 8inches of single cores outside of joint boxes.

Internal to vans ?? or outside coming in ??

No brown or blue leaving anywhere.

No change here then Dougie,

DB 7 circuits, nothing marked and no stickers and loose connections on loads of sockets light switches and also in CU.

Got feeling vans were done in a warehouse and thrown together in a afternoon.

What or who is the manufacturer would be worth a call to the company and ask for certification from the installation company if not name and shame IMO